Oscillation generator



Aug. &, 1933 w, E BOWER 1,921,501

OSCILLATION GENERATOR Filed July 24, 1950 5 Sheets-Sheet 1 Q [QMQQJ \1 gm l lalilmlalilslala 1N VEN TOR.

Wax u? fin www, wwvm ATTORNEY Aug 8, 1933 w. E. BQWER OSCILLATION GENERATOR 5 Sheets-Shet 2 Filed July 24, 1950 [NVEY TOR.

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A T TORNEY m n m Wei/m5 i7. @oww BY y 3 9 3 Qwm F I I I I H 1933' w. E. BOWER 1,921,501

OSCILLATION GENERATOR Filed July 24, 1950 5 Sheets-Sheet 3 A TORN E Y Aug. 8, 1933. w. E. BOWER 1,921,501

OSCILLATION GENERATOR Filed July 24, 1950 5 Sheets-Sheet 4 LU INVENTOR. D lg aw 9, boww, I ATTORNEY Aug. 8, 1933. w. E. BOWER 1,921,501

OSCILLATION GENERATOR Filed July 24, 1930 .5 Sheets-Sheet 5 IN VEN TOR. E

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TTORNEY tile-element with u -5 is a detai Patented Aug. &, 1953 v la earner caries 18 Claims.

. thereof for sustaining-constant frequency oscillations.

A further object of my invention is to pro: vide acoustic feed each system for synchroe nously exciting a mesh; .iicallyvibatile element for generating osci lation of constant frequency.

A still further object of my invention is to provide means for a mechanically vibraccrnpressional and rarefaction'il forces on oppos e faces I with the period of the elect erated by the mechanically vibratile element for susta n" oscillations a predetermined frequency.

Other and further objects of my invention reside in. the areal t of acoustically actuated niechanica y vibr V scent arranged to control an oscillator systc as set forth more iully in the specification he einafter following by reference to the accoi g drawings in which;

Figure 1 vicallyillustrates the electrical and acous lc feed-hack system of my invention; Fig. 2 shows a modified form my invention; -pull'systein of acoustic feed: back for sustaig oscillations generated by mechan cally atile element; Fig l shows c. form of nieunti for a crystale in nt employed in the oscillator; Fig.

de view of the crystal mounting employed in 6 shows a multiple generator system c. ocal -ng my invention; '7 shows a modified form-of acoustic feed-back system 2'". audio frequency oscillator.

My iven is directed to low frequency standard generator, having improved features of importance over oscillation ge erators heretofore available. oscillation generator system of my invention consists of an arrangement of acoustical coupling between the con trolling mechanical vibrating element the of oscillator circuit embodying Fig. 3 shows 2. pt

electrical system used to maintain the vibrations. By the device of my invention all electrical c0ntacts are eliminated and the controlling element left practically free to'execute its natural cs cillations ailected only by its intrinsic mechanical properties and the surrounding atmospheric conditions. The apparatus has a degree of accuracy in the maintenance of a given frequency much greater than has heretofore been possible.

Referring to Fig. 1 of the drawings, reference character 1G8 designatesv a v1orating element which may e in the of a bar, rod, disc, or cylinder supported in any convenient manner approximately symmetrically over the opening 03 an acoustical resonator indicated at 2. To this resonator are attached, as shown, two or more slabs of piezoelectric material represented atS and 4, which on being jarred by the vibrations. of the master vibrator 1G0, develop a piezoelectric voltage on the electrodes, 5, 6, 7, and 8; These electrodes are connected as shown through leads 1i and 12 betwee the grid and'cathode, elec. trodes of electron tube 31. The voltage. thus developed is amplified in any oneoi a number of well known methods of cascade amplification such as for example through the interconnected electron tube amplifier .21 havingtubes 32, 33 and 34. The output of the amplifieris made to 0pcrate a loud speaker unit 13, or its equivalent, and this in turn actuates the air column 14, connected to the resonator 2, and so adjusted in length as to give the proper phase for the feedback of energy to maintain the bar lilo in continuous vibration. y

The master vibrator 106, may be of any materia1 having suitable elastic constants such as metals, glass, or fused quartz. It may also be of any material showing piezoelectric effects, or of nonp'iezo electric material veneered. wholly or partially with piece-electrical rnaterial. In. the last two cases, the master-vibrator'must be so placed that th charges developed by its vibrations are so poled as to bring about a proper phase relation with. the feedback energy.

Vibrator ice is mounted on felt or cork pads 169a and 10912 at nodal points for the fundamental mode of vibration of bar l0O,'the projection of bar 169 on either side of the pads'being" approximately one fourth of the length L. Under some circumstances a well balanced bar suspended lightly by silk threads at nodal lines will vibrate when the acoustical resonator or source is removed far from the bar, say 10 feet or more. The resonator 2 may be provided with a metering hole 2a determined asto size applied as follows: I have shown the master vibrator 1, formed either from piezoelectric materia1, or of non-piezo-electric material veneered in whole or in part with piezoelectric The piezoelectric element may be hung by thre ds or supported in any other convenient manner as set forth in my copending application, Ser. No. 336,222 filed January 35, 1929, Patent No. l,8l5,- 324, granted September 6, 1932. The charges developed when this vibrator is put in action by tapping or otherwise, are by electrostatic induc tion communicated to the electrodes formed by plate 2a and resonator 2 as indicated by the dotted line condensers 35. These changes are amplified and fed back through the loud speakor unit 13 and the acoustical system as described in connection with Fig. l. V

The method of operation shown in Fig. 3 differs from that in Fig. 2 by the provision of a push-pull acoustical feed-back. A double tube system shown at 36 and 37 of insulation material or metal tubes insulated from the resonators connects to the loud speaker 13 and delivers sound waves to the resonator chambers 38 and 39 respectively. The piezoelectric bar 1 or ma vibrator is disposed between chambers 38 and 39 which serve as electrodes capacitively related to the faces of the piezoelectric crystal or master vibrator l as represented by dotted line condensers 35. The sound energy propagated through tube 37 is out of phase with the sound energy propagated through tube 36 by 180 phase when the sound reaches the'resonance chambers 39 38 for tube 37"is one half wave length longer than tube 36. Therefore, the compressions and rarefactions occur alternately and in synchronism for applying push-pull forces to the crystal or master vibrator l and maintain the in vibration;

Referring to Figs. 4 and 5, a method of applying the same principle is shown which differs from those described above, in that the master vibrator 1 which here must be of piezoelectric material, or of non-piezo-electric material veneered with piezoelectric material, is clamped symmetrically as shown between parts of a clamp 40, the two halves of the clamp 41 and 42 being insulated from each other and serving as collecting electrodes for the voltage developed by its vibrations. This voltage is then amplified and the energy necessary to sustain the vibrations fed back through a similar, though not identical, acoustical systen to that described above. The resonance chamber is shown at 43 connected through link 44 with the lower electrode 42. The resonance chamber 43 is supported by members 47 adjacent the end of the air column 14.

In any of these methods of applying the principle, an electric current of a frequency determined by the master vibrator can be derived from the secondary winding 45 of the transformer 20 whose primary 46 is inthe output of the last tube of the cascade amplifier. Connections may be taken from the secondary winding 45 of transformer 20 to any desired point of application for the constant frequency energy. In the methods of use, shown in Figs. 1, 2, and 3, the points of support for the vibratile or master vibrator element 1 should be at or near the nodes of the mechanical vibrations which it is desired to utilize. When the method is applied as shown in Figs. 4 and 5, the point of support is the center of the vibrator 1.

Since, by the methods of use shown in Figs. 1, 2, and 3, the vibrating element is constrained in no way by electrodes or otherwise, except by its own intrinsic elastic properties and the atmospheric conditions existing in its vicinity, and since these latter can be made to be subject to very accurate control, th s system affords a method of obtaining and maintaining a constant frequency Within the range of acoustical frequencies of a precision much greater than has heretofore been attained.

A further advantage of my system is that it is possible when operated in any one of the methods shown in Figs. 1, 2, and 3, to have two (or more) master vibrators simultaneously operating from the same acoustical feed-back system, provided the master vibrators do not differ too much in frequency. Thus, it is possible to obtain from the output the sum and difference frequencies of the vibrators, and hence the range of frequencies in which the method is applicable can be much extended.

In Fig. 6 I have schematically shown the essentials where 1' is a bar of metal treated or veneered with quartz or other piezoelectric material or genuine quartz bar may be employed and suspended at or near its nodes of free vibration in such a manner as to be free to oscillate in any of its nodes of vibration due to some external pulsing iorce loosely coupled thereto. Circuit 48 comprises an amplifier, the input circuit of which has the grid connected to electrode 51 on piezo-electric crystal 1 with connections from the opposite side of the input circuit to electrode 52 and to the resonance chamber 53 as shown.

Circuit 54 is an amolifiersimilar to amplifier 48. Electrode 55 on piezo-electric crystal or master vibrator 1 connects to the grid electrode of the first stage of amplification. The unit 13 is any of the well known loud speaker instrument and is here used to convert electrical energy into sound energy which is fed through the acoustical feed back tube 56 to supply energy to the acoustical resonator 53 in such a phase relation that if the crystal or master vibrator 1 or its equivalent is vibrating that said vibrations will be reinforced to such an extent that continuous oscillations are maintained at an amplitude proportional to the energy supplied by the acoustical system.

The bending of the master vibrator or piezoelectric generator 1 furnishes an electrostatic charge which fluctuates between minimum and is piezoelectric voltage collected by elecstatc coupling to the various electrodes causes an amplified grid voltage to operate in circuit 48 on the several tubes therein and in circuit 54 on several tubes therein, The currentthrough the output transformers 57 and 58 would normally be in exact phase relation. However, if in circuit 54 the electrode 55 which connects to the grid and the electrodes 52 and 53 which connect to the filament are reversed; via, 55 terminating to the filament and 52 and 53 to the grid, then the out- The acoustic feed-back arrangement is modifled by'the addition. of an adjustable yoke 61 which is telescopically slidable over. tubular members 62 and 63,]which slide into theends oftubes 63 and 69 oi the acoustic feed-back 'systern. A bridge member 65 connects across tubes 68 and 69 and carries an extension 66 thereon throughwhich the screw threaded member 64 passes. The screw threaded member 64 is en.- gaged bythe knurled thumb screw 67, for advancing the yoke 61 toward or away from tubu lar members 68 and '69. screw 64 rotatably engages the socket 63'at the end of the yoke. In thismanner the-acoustic feed-back between electromagnetic sound repro ducer l3 and resonance chamber 53 isvaried. By adjustably tuning the acoustic feed-back system by selectively" positioning thejyoke 61 with respect to the tubular members -621and 63, Ilam enabled to accuratelyadjust the acoustic system to the fundamental frequency of the mechanically vibratile element. While I'have illustrated fixed air columns in the other figures of the drawings, it will be understood that the length of such'air columns andresonatorswas originally determined by a tuning process. In order to increasethe accuracy of the oscillator, I may introduce adjustable means for. selectively fixing the length of the aircolulnn. The amplitude of the movement of the mechanically vibratile'element is brought up to a maximum when the resonance chamber and air column are ad- .justed to the. precise length corresponding to the fundamental frequency of the mechanically vibratile element. I

I have found the acoustic feed-back principle as applied to'a piezoelectric crystal controlled oscillator system highly efilcient'in its operation and accurate in its maintenance of constant frequency. While I have described my invention in certain of its preferred embodiments I desire that it be understood that modifications maybe made and that no limitations upon my invention are intended other than are imposed byv the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States "is as follows:

1. A generator of electrical oscillations comprising a piezoelectric element, means for supporting said piezoelectric crystal element for vibratory movement, anainplification system including an input circuit and an'outputnit, connections between said piezoelectric element and said input circuit, an electromagnetic sound. reproducer connected in. said output circuit, and 7 I means acoustically coupling saidsound reproducer with opposite sides of said rnechanically means fior acoustically coupling said electromagnetic sound reproducer to said piezoelectric element for applyingacoustic impulses against said piezoelectric crystal element in synchronism vwith the electrical impulses generated by said piezoelectric element for reinforcing the vibrations of The end or" adjusting frequency said piezoelectric crystal' at'constant frequency.

2. A generatorof electrical oscillations com prising a mechanically vibratile element, means for suspending said element for vihratorynzovement, an electrical oscillatory circuit connected with saidvibratile element, an electromagnetic sound reproduccr energized by said circuit, and means for acoustically coupling said sound r'eproducer wi h said mechanically vibratileelcment for feeding back sound vibrations upon opposite sides of said mechanically vibratile element in cooperative phase relation for synchronously reinforcing and maintaining the oscillations in said circuit substantially constant- 3. A generator of electrical oscillations com prising a mechanically vibratile element, means for: suspending said mechanically vibratile element for vibratory movement, an electron tube amplification system having an input circuit and an output circuit, connections between said input circuit and said mechanically vibratile ele-,

merit for sustaining. electricaloscillations at a frequency determined by the characteristics of said mechanically'vibratile element, a'soundreproducer connected with said output circuit, and means acoustically coupling said sound reproducer withopposite sides of said mechanically ,vibratile element for subjecting said mechanically vibratiie element tosound vibrations in cooperative phase relation at each side thereof in I step with the mechanical vibrations ofsaid mechanically vibratile element for maintaining the oscillations in said amplification system substantially constant. i

4. An oscillation generator comprising a mechanically vibratile, element, an amplification system havini an input circuit and an output circuit, connections between said mechanically vibratile elementand said input circuit, a tone electromagnetic sound reproducer connected, in Qsaid output circuit, and means opposite sidesof said mechanically vibratile element for alternately subjecting said inechanica.,- ly vibratile element to compressional and rareice acoustically couplingsaidsound reproducer with factional forces insynchronism with the-oscil laticn characteristics of said mechanically vibratile element, whereby oscillations 'of constant frequency are sustained through said amplification system. f

5; An oscillation generator comprising an electron tube system having an input circuit, a work circuit, an electromagnetic soundreproducer connectedin said work cuit, a piezoelectric crystal element connected in said input circuit for generating electricaloscillations; and

means acoustically coupling said'eie'ctrornagnetic sound reproducer'withopposite sides" of piezoelectric crystal element in cooperative phase relation for reini ing/the vibratory movement of whereby osci sustained in work circuit.

"6. An oscillation generator comprising amechanicallyyibratile element, an electrical circuitincluding said element, a sound reproducer connected, in said electrical circuit, a work circuit connected to said electrical circuit, and

vibratile element for subjecting said mechanical- "ly' vibratile elementto the efiects of sound vibrations indiflerent phase relations for sustaintrio crystal element, -lOllS or constant frequency are 7. Anoscillation generator comprising a mechanically vibratile element, a pair of resonance chambers disposed on opposite sides of said mechanically vibratile element, a sound reproducer connected with said resonance chambers for supplying sound vibrations to said resonance chambers in different phase relations, a circuit coupling said mechanically vibratile element with said electromagnetic sound reproducer for effecting a continuous feed back of electrical and acoustic energy, and a work circuit connected with said aforesaid circuit for sustaining oscillations at substantially constant frequency.

8. An oscillation generator comprising a piezo electric crystal element, means for suspending said piezoelectric crystal element for vibratory movement, a circuit connected with said element for sustaining oscillations generated by said piezoelectric crystal element, an electromagnetic sound reproducer connected with said circuit for reproducing sound vibrations corresponding to the oscillations generated by said piezoelectric crystal element and means for applying acoustic vibrations developed by said sound reproducer to opposite sides of said piezoelectric crystal element in cooperative phase relation for sustaining oscillations in said circuit at constant frequency. V

,9. An oscillation generator comprising a piezo electric crystal element, a circuit for sustaining oscillations generated by said piezo electric crystal element, and means for regeneratively applying acoustic vibrations to opposite sides or said piezoelectric crystal element in different phase relations for sustaining oscillations at substantially constant frequency.

10. A piezoelectric crystal apparatus including a piezoelectric crystal element, electrodes capacitatively related to said piezoelectric crystal element, each of said electrodes comprising substantially hollow resonance chambers, and means for imparting sound vibrations through said resonance chambers against said piezoelectriccrystal element.

a multiplicity of piezoelectric crystal elements, a

resonance chamber, means extending from said resonance chamber and supporting said piezoelectric crystal elements and establishing electrical connection with one surface of each of said.

piezoelectric crystal elements, means, establishing electrical connection with the opposite surfaces of said piezoelectric crystal elements, a' sound generator controlled by said piezoelectric crystal elements, and means for introducing sound vibrations from said sound generator through said resonance chamber for simultaneously subjecting said piezoelectric crystal elements'to acoustic vibrations proportional to the natural period of said piezoelectric crystal elements and in synchronism with the operation thereof.

13. Piezoelectric crystal apparatus comprising a multiplicity of piezoelectric crystal elements, a resonance chamber constituting one electrode for said crystal elements, means for supporting said piezoelectric crystal elements with respectto said resonance chamber, separate mechanical means interconnecting said piezoelectric crystal elements adjacent said supporting means, electrodes for establishing electrical connection with they surfaces of said piezoelectric crystal elements, a

sound generator controlled by said piezoelectric crystal elements and a sound conveying tube acoustically connected with said sound generator for introducing sound vibrations through said resonance chamber in proportion to the natural period of said piezoelectric crystal elements.

14. An oscillation generator comprising a mechanically vibratile element, a pair of independ ent amplifier circuits, a separate work circuit connected with each of said amplifier circuits, an electromagnetic sound reproducer connected to the output circuit of one of said amplifier circuits, individual connections between said mechanically vibratile element and the input circuits of said amplifier circuits, and an'acoustic coupling between said sound reproducer and said mechanically vibratile element, whereby oscillations are generated in one work circuit in outer phase relation to theoscillations generated in the other work circuit. 7

15. In an oscillation generator, a piezoelectric crystal element, a pair of independent amplifier circuits, means connecting the input circuits of each of said amplifiercircuits with said piezoelectric crystal element in out of phase relation, separate work circuits connected with each of said amplifier circuits, a loud speaker reproducer connected to the output circuit of one of said amplifier circuits, and means acoustically coupling said loud speaker reproducer with said piezoelectric crystal element for regeneratively sustaining oscillations and impressing the oscillations thus sustained upon said separate work circuits at substantially constant frequency in out of phase relation.

16. An oscillation generator comprising a piezoelectric crystal element adaptedto generate a fundamental frequency and harmonics and multiples thereof, an amplification circuit electrodes disposed adjacent said piezoelectric crystalelement and connected to the input of said amplification Circuit, a workcircuit connected with said amplification circuit, an electromagnetic sound reproducer connected in the output circuit of said amplification circuit, and means for acoustically coupling said electromagnetic sound reproducer with said piezoelectric crystal element for subjecting said piezoelectric crystal element to sound vibrations in synchronism With'the self-vibration of said piezoelectric crystal element and sustaining oscillations of constant frequency in said work circuit.

1'7. An oscillation generator comprising a piezoelectric crystal element, means for mounting said piezo electric crystal element for vibration, an amplification circuit, a work circuit connected therewith, an electromagnetic sound reproducer connected with the output circuit of said amplification circuit, electrodes disposed adjacent said piezoelectric crystal element and connected with the input circuit of said amplification circuit, one of said electrodes being constituted by a substan tially hollow resonance chamber, and adjustable means acoustically coupling said electromagnetic sound reproducer with said resonance chamber for impressing sound vibrations upon said piezoelectric crystal element in step with the natural vibration thereof and reinforcing the operation of said crystal element for establishing ing the oscillations thus for sustaining oscillations under control of said I piezoelectric crystal element, a sound generating device connected in the output of said electron tube system, means acoustically coupling said sound generating device with the resonance chamber electrode adjacent said piezo electric crystal element for directing sound vibrations upon said piezoelectric crystal and reinforcing the movement thereof, and'a work circuit connected with said'electron tube system for utilizgenerated.

WARD E. BOWER. 

